Magnetic journalling technology opens up fields of application of machine and apparatus construction with extremely high requirements on the speed of rotation region, the lifetime, the purity and the sealing tightness of the drive system--thus substantially fields of application which can not or can only with difficulty be realised using conventional journalling techniques. Various embodiments, such as for example high speed milling and grinding spindles, turbocompressors, vacuum pumps, or pumps for chemical or medical products of high purity are already being equipped with magnetic bearings.
A conventional magnetically journalled electrical machine (FIG. 1) requires, in addition to a machine unit 1, two radial magnetic bearings 2 and 3 respectively, an axial magnetic bearing 4, two mechanical interception bearings 5 and 6 respectively and a total of thirteen power controllers 7, 8, 9 and 10 for the excitation of the motoric and magnetic bearing loops.
There are proposals (FIG. 2) in the literature for integrating machine and radial magnetic bearings in a magnetic stator unit. Two separate winding systems 11 and 12 for the torque and suspension force winding are inserted into multiply layered into grooves in a stator. Both winding systems are three-looped and differ by one in the number of pole pairs. The coils are distributed over a plurality of grooves. The example of FIG. 2 shows:
a four-pole machine winding 11 (outside): first loop 13, second loop 14, third loop 15 PA1 a two-pole suspension winding 12 (inside): first loop 16, second loop 17, third loop 18.
The arrows (without reference symbols) from the rotor in the direction towards the stator or from the stator in the direction towards the rotor stand for the direction of the magnetisation of the four magnetic rotor segments (e.g. radial or diametral magnetisation).
In applications which require no rigid-axis rotor guidance, such as for example in ventilators, fans, pumps or mixers, the axial magnetic bearing and the second radial magnetic bearing can be omitted from the integrated machine-magnetic-bearing embodiment. A prerequisite for this is a disc-shaped embodiment of the rotor with a length dimension (FIG. 3) which is small with respect to the rotor diameter. Thus a passive stabilization of the rotor position in the axial direction and the tilt directions can be achieved via the magnetic traction 41 between the stator 39 and the rotor 40.
In many cases however the complicated and expensive system construction and therewith the higher manufacturing costs stand in the way of the technical use of magnetic journalling. The object of the invention consists therefore in the simplification of the mechanical construction of the machine and magnetic bearing unit taking into consideration the electronic excitation which is suitable for this.